Trust management is directed to the concept of controlling decisions made by system components such as applications with respect to certain potentially dangerous actions. In general, to make an appropriate decision, an application's desired action is verified against a policy. A policy for a particular action is a set of rules that determine whether that particular action is allowed or denied. By way of example, a web browser may make a decision on whether to download executable code from the Internet based on a policy comprising explicit user preferences and the validity of a digital signature on the code. Similarly, a certificate authority makes a decision whether to issue a certificate based on whether the requestor complies with its policy for establishing its identity, while a secure operating system such as Microsoft Windows NT decides whether to log on a user based on a policy of whether the correct account password was supplied, the account is not locked out and whether other constraints, such as logon time and date restrictions, are not violated.
However, although in general the operation of verifying a request for action against a policy is common to trust management in applications, policy evaluation implementations are different in each application. For example, policies are represented in different ways in each application, and sometimes difficult for users to locate or recognize. Moreover, because the policies are built into the applications, the policies are essentially static and only minimally modifiable as limited by a few optional settings. As a result, there is no easy way to modify or add new policy constraints to policies used by applications to control their decisions, nor is there an easy way to enforce new domain-wide policies. Administrators of large (enterprise) networks are often forced to go to great lengths to uniformly implement policies.